Plasma processing apparatus

ABSTRACT

A plasma processing apparatus provided with a holding stage of a system in which a temperature of an electrode block is controlled so as to control the temperature of a semiconductor wafer. The electrode block is provided with at least first and second independent temperature controllers on inner and outer sides thereof, and a slit for suppressing heat transfer is provided in the electrode block between the first and second temperature controllers.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. application Ser. No. 10/083,381, filedFeb. 27, 2002, now U.S. Pat. No. 6.664.738, the subject matter of whichis incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates to a plasma processing apparatus appliedto microfabrication in semiconductor fabricating processes or the likeand, more particularly, to a plasma processing apparatus provided with aholding stage on which a semiconductor wafer is to be placed.

With the trend toward high integration design of semiconductor devicesbecoming remarkable in recent years, ever-increasing miniaturization ofcircuit patterns has been demanded and dimensional fabrication accuracyrequired has been increasingly severe. Moreover, at the same time, ithas become necessary to meet requirements for improved throughput andlarger areas of workpieces to be treated and the temperaturecontrollability of semiconductor wafers during processing has becomevery important.

For example, in an etching process that requires a high aspect ratio(fine and deep trenches), anisotropic etching is required and in orderto realize this, a process in which etching is performed whileprotecting side walls with an organic polymer is adopted and, in thiscase, the generation of an organic polymer that provides protectivefilms varies depending on temperature. If the temperature within asemiconductor wafer during etching processing is nonuniformlydistributed, the degree of formation of side wall protecting filmsvaries in the wafer plane, with the result that etching shape also maysometimes become nonuniform, thus posing a problem.

Also, there is a case where reaction products adhere to etched surfacesagain, thereby lowering etching rates. The reaction products are apt tobe distributed more at the center of a semiconductor wafer than near theouter periphery of the semiconductor wafer, with the result that theetching rate is lower at the center of the semiconductor wafer than nearthe outer periphery and, therefore, the etching shape within thesemiconductor wafer plane deviates.

In order to improve this, it is effective to adopt a method by which there-adhering of reaction products is suppressed by raising thetemperature near the center of a wafer in comparison with thetemperature near the outer periphery. Therefore, as described above, itis necessary to control the semiconductor wafer temperature duringplasma etching so that it is uniform in the wafer plane or to cancel outthe distribution of reaction products by intentionally raising thetemperature in the plane of a semiconductor wafer at the center or nearthe outer periphery.

Incidentally, it is a general practice to realize the semiconductorwafer temperature control during processing by controlling the surfaceof an electrostatic chuck (a holding stage) on which the wafer to betreated is placed, and as a method of temperature control for such asemiconductor wafer during processing, a technique disclosed inJP-A-2000-216140 (prior art 1), for example, can be mentioned.

In this prior art 1, there is disclosed a structure such that aplurality of independent coolant flow paths capable of controlling theflow rate of coolant are provided within an electrostatic electrodeblock that constitutes a holding stage and the electrode block surfaceis coated with a dielectric film.

Furthermore, in JP-A-9-17770 (prior art 2) is disclosed a structure suchthat in order to control the in-plane temperature distribution of asemiconductor wafer, two systems of coolant flow path are provided onconcentric circles in the interior of an electrostatic chuck, whereby arelatively low-temperature coolant is caused to circulate in an outercoolant flow path and a relatively high-temperature coolant is caused tocirculate in an inner coolant flow path. In JP-A-845909 (prior art 3) isdisclosed a sample bed (a holding stage) of such a structure that ametal electrode block is divided into portions, in each of which acoolant flow path or a heater is provided to perform temperaturecontrol.

In the above prior arts, consideration is not given to the flow of heatin an electrostatic chuck and there was a problem in positivelyrealizing a clear temperature distribution.

For examples, in the prior arts 1 and 2, in order to realize atemperature distribution in which the temperature near the center of asemiconductor wafer during processing is set higher than the temperaturenear the outer periphery of the wafer, the temperature or flow rate of acoolant is controlled. However, a clear in-plane temperaturedistribution cannot be obtained because of the thermal conductivity ofthe electrode block and, at the same time, because coolant flow pathsare adjacent to each other, the temperature is made uniform within theelectrode block, making it further impossible to obtain a cleartemperature distribution.

On the other hand, in the electrostatic chuck disclosed as the prior art3, independent temperature control is possible within divided electrodeblocks and in-plane temperature distribution control is accomplished.However, because there is a gap between the blocks, it is difficult toform dielectric films of thin film thickness with good reliability.

Also, in the prior art 1, the electrode is fixed by means of screws onlyin the circumferential part and, therefore, the electrode block isdeformed in convex shape by the pressure of the coolant, with the resultthat in some cases it is impossible to uniformly adsorb thesemiconductor wafer and an undesired temperature distribution isgenerated in the plane of the semiconductor wafer.

SUMMARY OF THE INVENTION

The object of the invention is to provide a plasma processing apparatuscapable of positively controlling the temperature distribution of asemiconductor wafer during etching processing in a clear state.

The above-described object can be achieved by using a plasma processingapparatus provided with a holding stage of a method by which thetemperature of an electrode block is controlled thereby to control thetemperature of a semiconductor wafer. In this holding stage, theelectrode block is provided with independent temperature control meanson the inner and outer sides and, at the same time, a slit forsuppressing heat transfer is provided between these temperature controlmeans.

In this plasma processing apparatus, the above-described slit forsuppressing heat transfer may be formed almost concentrically.

Also, the above-described object can be achieved by using a plasmaprocessing apparatus, in which the above-described independenttemperature control means on the inner and outer sides may comprise: afirst flow path and a second flow path, which are provided in theelectrode block independently on the inner and outer sides of theelectrode block; and first heat-medium supply means and secondheat-medium supply means, which independently supply to these first andsecond flow paths a heat medium, for which at least either oftemperature and flow rate is controlled. Similarly, the above-describedobject can be achieved by using a plasma processing apparatus, in whichabove-described independent temperature control means on the inner andouter sides may comprise: a first flow path and a second flow path,which are provided in the above-described electrode block independentlyon the inner and outer sides of the electrode block; first heat-mediumsupply means and second heat-medium supply means, which commonly supplyto these first and second flow paths a heat medium, for which at leasteither of temperature and flow rate is controlled; and temperatureadjustment means provided in a conduit that connects the above-describedfirst and second flow paths together.

Furthermore, the above-described temperature adjustment means may beconstituted by a heater, and this heater may be provided on the backsideof the above-described electrode block or may be built in theabove-described electrode block.

Next, the above-described electrode block may be provided, on itssurface, with a dielectric film, and a heater may be built within thedielectric film. The above-described heater may serve also as anelectrostatic chuck.

Also, the above-described electrode block may comprise one member inwhich the above-described heat-medium flow paths are formed and theother member for ensuring the rigidity of the above-described electrodeblock, and these members may be fastened in one piece. Means forfastening the above-described two members may be any of screwing,brazing, diffusion bonding and electron beam welding. Moreover, themember for ensuring rigidity may be made of a material with a lowerthermal conductivity than the above-described electrode block.

Or the above-described first and second flow paths may be each formedfrom a pipe with a circular section or a polygonal shape attached to theabove-described electrode block. Moreover, the above-described pipe maybe built in the above-described electrode block.

Also, the above-described electrode block may be provided with at leastthree temperature sensors and temperature control may be performed onthe basis of information from these temperature sensors. Theabove-described electrode block may be provided, on its surface, with adielectric film and may be constructed as an electrostatic chuck inwhich a gas for heat transfer is introduced to between theabove-described dielectric film and the above-described semiconductorwafer.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory drawing of an embodiment of a plasma processingapparatus according to the invention;

FIG. 2 is a perspective view of an embodiment of an electrostatic chuckin a plasma processing apparatus according to the invention;

FIG. 3 is an explanatory drawing of the slit arrangement state inanother embodiment of an electrostatic chuck according to the invention;

FIG. 4 is explanatory drawing of the alit arrangement state in a furtherembodiment of an electrostatic chuck according to the invention;

FIG. 5 is a characteristic diagram of an example of pressuredistribution of helium gas between an electrostatic chuck and asemiconductor wafer;

FIG. 6 is a characteristic diagram of an example of the surfacetemperature of a semiconductor wafer by an electrostatic chuck;

FIG. 7 is a characteristic diagram of an example of the surfacetemperature of a semiconductor wafer in an embodiment of anelectrostatic chuck according to the invention as compared with priorart;

FIG. 8 is a characteristic diagram of an example of the surfacetemperature of a dielectric film in an embodiment of an electrostaticchuck according to the invention as compared with prior art;

FIG. 9 is a sectional view of the second embodiment of an electrostaticchuck according to the invention;

FIG. 10 is a sectional view of the third embodiment of an electrostaticchuck according to the invention;

FIG. 11A is an explanatory drawing of an example of deformation thatoccurs in an electrode block of an electrostatic chuck according to theinvention, which shows a state before deformation;

FIG. 11B is an explanatory drawing of an example of deformation thatoccurs in an electrode block of an electrostatic chuck according to theinvention, which shows a state after deformation;

FIG. 12 is an explanatory drawing of another example of deformation thatoccurs in an electrode block of an electrostatic chuck according to theinvention;

FIG. 13 is a sectional view of the fourth embodiment of an electrostaticchuck according to the invention; and

FIG. 14 is a sectional view of the fifth embodiment of an electrostaticchuck according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A plasma processing apparatus according to the invention will bedescribed below in detail with the aid of the illustrated embodiments.

FIG. 1 shows an embodiment of a plasma processing apparatus P accordingto the invention, and FIG. 2 is a perspective view, partially insection, of an electrostatic chuck S, which is used in this plasmaprocessing device as a holding stage S for a semiconductor wafer W.Incidentally, this holding stage is generally called an electrostaticchuck and hence is hereinafter referred to as an electrostatic chuck S.

And in the case of the electrostatic chuck S related to this embodiment,as will be described later with the aid of FIGS. 3 and 4, flow paths fora fluid (a heat medium) that works as a coolant or heat medium and, asshown in FIG. 1, this electrostatic chuck S is installed and used in aplasma processing device related to an embodiment of the invention.

As shown in FIG. 2, this electrostatic chuck S is constituted by anelectrode block 1 made of aluminum having a thickness of 25 mm, a guidemember 2 made of a stainless steel having a thickness of 10 mm, a basemember 3 having a thickness of 10 mm, a dielectric film 4, and anelectrode cover 5 made of ceramics, and is fabricated to have a diameterof 320 mm and a total thickness of 45 mm when it is intended for use ina semiconductor wafer of 12 inches (300 mm) in diameter, for example.

First, as shown in FIG. 3, on the undersurface of the electrode block 1are formed flow-path slits 11, 12 that are disposed in spiral form insuch a manner that the two constitute, respectively, a slit on theinside diameter side and a slit on the outside diameter side, andbetween the two slits 11, 12 is formed an almost concentric slit forsuppressing heat transfer 13 (radius=90 mm, width=5 mm, height(depth)=18 mm).

And upon the undersurface of this electrode block 1 is superposed theguide member 2, and the open portions of each slit 11, 12, 13 areblocked by fixing the guide member 2 with bolts 6. A gas introductionhole 7 is provided in such a manner that the gas introduction hole 7passes through the electrode block 1 and guide member 2 including thebase member 3.

Next, the dielectric film 4 is formed, for example, from high-purityalumina ceramics and its thickness is 0.1 mm. However, the material andthickness of this dielectric film 4 are not limited to this example andin the case of synthetic resins, for example, a thickness from 0.1 mm toa few millimeters can be selected according to the dielectric constantof the material.

And as shown in FIG. 2, this dielectric film 4 is provided with a linearslit 41, which extends radially while communicating with the gasintroduction hole 7, and a plurality of concentric slits 42 thatcommunicate with this linear slit 41, whereby it is ensured that whenthe semiconductor wafer W is placed on the electrostatic chuck S, heliumgas is introduced from the gas introduction hole 7 into a gap betweenthe dielectric film 4 and the semiconductor wafer W.

Each of the flow-path slits 11, 12 of the electrode block 1 is providedwith introduction portions 11A, 12A and discharge portions 11B, 12B fora coolant (or a heat medium), whereby each of the flow-path slits 11, 12can work as mutually independent heat-medium flow paths for the passageof a coolant for temperature control. And the introduction portions 11A,12A and discharge portions 11B, 12B of each of the flow-path slits 11,12 are connected to coolant supply units 51, 52, which are respectivelyindependent, so that at least either of the flow rate and temperature ofthe coolant to be circulated to each of the flow-path slits 11, 12 canbe individually adjusted.

The arrangement of the flow-path slits 11, 12 is not limited to thespiral shape shown here. For example, FIG. 4 shows a case where theflow-path slits 11, 12 are each arranged in a plurality of concentriccircles, and in this case a coolant flows in semicircular directionsthat are mutually counter directions.

Next, the operation of a plasma processing apparatus according to thisembodiment will be described. First, the electrostatic chuck S isinstalled within the processing chamber shown in FIG. 1, thesemiconductor wafer W is placed on the electrostatic chuck S, achlorine-based or fluorine-based gas is introduced, the atmosphere inthe processing chamber is irradiated with a microwave 9 generated by amagnetron 8 thereby to excite a plasma, and the distribution and densityof the plasma are controlled by a magnetic field generated by solenoidcoils 10.

And at the same time, etching is performed by applying a DC current anda high frequency to the electrode block 1 of electrostatic chuck S (FIG.2) while controlling the temperature of the semiconductor wafer W.

Incidentally, the embodiment of the plasma processing apparatusaccording to the invention is not limited to the method based on the useof a magnetron described here, and a plasma processing device of othermethods may be used.

Next, for the operation of the electrostatic chuck in this embodiment,the principle of temperature control will be first described below.

First, this electrostatic chuck S adsorbs the semiconductor wafer W by aCoulomb force or a Johnsen-Rahbeck force that is generated by theapplication of a high voltage to the dielectric film 4. There are twotypes of methods of application of a high voltage, i.e., the unipolartype and bipolar type. In the unipolar type, a uniform voltage isapplied across the semiconductor wafer and the dielectric film, whereasin the bipolar type, two or more kinds of electric potentials areapplied across the semiconductor wafer and the dielectric film. In thisembodiment, either of the two types may be used.

After adsorption, as described above, helium gas for heat transfer(usually, 1000 Pa or so) is introduced from the gas introduction hole 7into a gap between the semiconductor wafer W and the dielectric film 4.The temperature of the semiconductor wafer W is governed by the heatinput from the plasma, the overall heat transfer coefficient of the gapfilled with He gas, the thermal resistance of the electrode block 1, andthe overall heat transfer coefficient between the coolant that is causedto circulate into the electrode block 1 and the electrode block 1.

Therefore, the control of the temperature of the semiconductor wafer Wcan be performed either by installing a mechanism for changing thepressure of helium gas on the electrostatic chuck S, the temperature ofthe coolant, the flow rate of the coolant (a change in the overall heattransfer coefficient between the coolant and the electrode block) or byinstalling a second temperature adjustment mechanism such as a heater.

For example, in a case where the size of the flow-path slits 11, 12 is 5mm width×16 mm height, it has been ascertained that if the flow rate ofa coolant at 20° C. is doubled from 2 l/min to 4 l/min, then the overallheat transfer coefficient between the coolant and the electrode block 1increases from about 200 W/m2K to about 400 W/m2K. Therefore, becausethe overall heat transfer coefficient can be increased by increasing theflow rate of the coolant, a temperature rise of the electrode block 1can be held to a low level even if the heat input from the plasmaincreases.

Incidentally, in a general electrostatic chuck, for reasons of itsstructure a temperature distribution occurs in the plane of asemiconductor wafer as described below in spite of uniform heat inputfrom a plasma. Because the pressure of helium gas introduced into a gapbetween the semiconductor wafer and a dielectric film is higher than thepressure in the chamber (processing chamber) during the generation of aplasma, the gas leaks from the outermost peripheral part of thesemiconductor wafer W. The measured volume of leaking gas is 2 to 5ml/min.

FIG. 5 shows an example of calculation result of helium gas pressure. Inthis graph are shown calculated values of pressure distribution on thebackside of a semiconductor wafer found from the leak rate of heliumgas. As shown in this figure, because the helium gas pressure at theoutermost periphery of the semiconductor wafer is higher than thechamber pressure during the generation of a plasma, the helium gaspressure drops abruptly at the outer periphery of the semiconductorwafer.

Next, FIG. 6 shows the surface temperature of the semiconductor wafer Win a case where heat input is uniform in the plane of the semiconductorwafer. In FIG. 1 are shown results obtained in a case where a plasma isgenerated in an atmosphere into which a fluorine-based gas (pressure 1Pa) is introduced by use of the plasma processing apparatus shown inFIG. 1 and where the flow rate of the coolant is set at 5 l/min and thetemperature of the coolant is set at 35° C. The abscissa indicates thedistance from the center of the semiconductor wafer and the ordinateindicates the temperature of the semiconductor wafer surface. The mark •denotes measured values and the solid line represents calculated values.

Therefore, from FIGS. 5 and 6, it is apparent that the surfacetemperature of the semiconductor is higher at the outermost peripherythan at the center.

Next, the temperature difference in the plane of the semiconductorwafer, which is denoted by ΔT, depends mainly on high-frequency electricpower applied to the electrostatic chuck, and reached about 10° C. whenpower of 1300 W, for example, was applied.

Therefore, in order to give a gentle temperature distribution (forexample, the temperature at the center or at the periphery is high) onthe plane of the semiconductor wafer by means of the electrostaticchuck, it is necessary to control the temperature distribution inconsideration of the pressure distribution of helium gas.

Incidentally, the foregoing applies to general electrostatic chucksincluding prior art. Next, an explanation will be given to theelectrostatic chuck S related to the embodiment of the invention shownin FIG. 1. In this embodiment, the electrode block 1 that constitutesthis electrostatic chuck S is provided with the slit for suppressingheat transfer 13 in such a manner that the slit 13 defines a boundarybetween the inner and outer peripheral parts of the electrode block 1.

Furthermore, in this electrostatic chuck S, the electrode block 1 isprovided with the independent flow-path slit 11 and flow-path slit 12 insuch a manner that the flow-path slits 11 and 12 sandwich the slit forsuppressing heat transfer 13 on the inner and outer peripheral sides,and at least either of the flow rate and temperature of the coolant canbe individually adjusted.

The slit for suppressing heat transfer 13 is kept blocked by the guidemember 2 as described above and, therefore, the interior of the slit forsuppressing heat transfer 13 is filled with an atmosphere at a pressurealmost equal to the pressure in the processing chamber or is kept in avacuum. For this reason, the slit for suppressing heat transfer 13suppresses heat transfer between the inner and outer peripheral sides ofthe electrode block 1, thus allowing a large temperature differencebetween the two sides to occur.

FIG. 7 shows an example of measurement of the surface temperaturedistribution of a semiconductor wafer W obtained under the sameconditions as in FIG. 6 by use of an electrostatic chuck S that isprovided, in the electrode block 1, with the slit for suppressing heattransfer 13. In this example, a case where the temperature in the centerpart is set relatively higher than the temperature in the outerperipheral part is supposed. In this example, the high-frequencyelectric power applied to the electrostatic chuck is 100 to 1300 W, thecoolant flow rate in the slit 11 is 1 to 4 l/min, and the coolant flowrate in the slit 12 is 4 to 8 l/min.

As shown in FIG. 7, it is apparent that in the electrostatic chuck Sthat is provided with the slit for suppressing heat transfer 13 as oneembodiment of the invention, the temperature in the center part can beraised sufficiently high while holding the temperature of the outermostperipheral part of the surface of the semiconductor wafer W to a lowlevel.

Next, FIG. 8 shows the result of an analysis of the surface temperatureof the dielectric film 4. As shown in the figure, the slit forsuppressing heat transfer 13 is provided also in this case and,therefore, the temperature distribution of the surface of dielectricfilm 4 is remarkable. Therefore, it is apparent that a very distincttemperature distribution was obtained. It is also apparent that thetemperature distribution changes greatly on both sides of the slit forsuppressing heat transfer 13.

In this type of electrostatic chuck, as described above, it is a generalphenomenon that the helium gas pressure is low in the outermostperipheral part of the semiconductor wafer and that the temperature ishigh in the outermost peripheral part of the semiconductor wafer.Therefore, in the case of this embodiment, in order to hold thetemperature of the outermost peripheral part of the semiconductor waferW to a low level and, at the same time, to raise the temperature in thecenter part, it is necessary to install the slit for suppressing heattransfer 13 in an appropriate position.

In this embodiment, good results were obtained by setting the positionof the slit for suppressing heat transfer 13 intended for use, forexample, in the above-described semiconductor wafer with a diameter of300 mm in the range of 80 to 120 mm from the center. In the case of asemiconductor wafer W having a diameter of 200 mm, this range is 60 to80 mm.

Therefore, as is apparent from these results, in the electrostatic chuckS according to the embodiment of the invention, it is preferred that theslit for suppressing heat transfer 13 be provided in the range of 50 to80% of the radius of the electrode block 1.

Incidentally, a temperature distribution desired for semiconductorwafers in plasma processing is usually a gentle circumferentialdistribution in which the temperature in the center part or in the outerperipheral part is high, and for this reason, it is preferred that theslit for suppressing heat transfer 13 of electrostatic chuck S beconcentrically formed.

On the other hand, it is preferred that the sectional shape of this slitfor suppressing heat transfer 13 be rectangular, trapezoidal, etc. fromthe standpoint of fabrication. It is the dimension of height of thesectional shape that is important, and the higher the height, that is,the more the height of the slit for suppressing heat transfer 13.

The more the effect of this slit to suppress heat transfer willincrease. However, when the height of the slit for suppressing heattransfer 13 increases in this manner, the rigidity of the electrodeblock 1 decreases. In this case, therefore, a rib may be provided in theslit thereby to prevent a decrease in the rigidity of the electrodeblock 1.

Therefore, according to this embodiment of the invention, it is possibleto clearly control the temperature distribution of the semiconductorwafer W during plasma etching, with the result that through arbitrarytemperature control it is possible to ensure a uniform temperature inthe plane of the semiconductor wafer or a temperature distribution in aclear state, such as a temperature distribution pattern in which thetemperature in the center portion or a temperature distribution patternin which the temperature in the outer peripheral portion is high. As aresult, this embodiment of the invention can be easily applied to plasmaprocessing in which by canceling out the distribution of reactionproducts the re-adhering of the reaction products to etched surfaces issuppressed, thus contributing greatly to an improvement in the yield ofsemiconductor wafer processing.

Next, further embodiments of the invention will be described below.First, FIG. 9 shows an electrostatic chuck in the second embodiment ofthe invention. In this embodiment, a slit for suppressing heat transfer13 is provided in an electrode block 1, a slit 11, which provides acoolant flow path on the inner peripheral side, and a slit 12, whichprovides a coolant flow path on the inner peripheral side, are connectedin series by means of a conduit 14, and an electric heater 15 isprovided in this conduit 14 to constitute an electrostatic chuck S1.

And in this electrostatic chuck S1, a coolant is supplied from onecoolant supply unit 53 commonly to the slit 11 and slit 12, which arethe coolant flow paths in the electrode block 1. During coolant supply,the temperature is controlled by a power controller, which is not shownin the figure, and the heater 15 works to heat the coolant flowingthrough the conduit 14 to a prescribed temperature.

Therefore, according to this electrostatic chuck S1, by adjusting theheating temperature of the coolant by the heater 15, the temperaturedistribution of the semiconductor wafer W can be easily changed to atemperature distribution pattern in which the temperature in the centerpart is high or a temperature distribution pattern in which thetemperature in the outer peripheral part is high.

That is, when the temperature distribution of the semiconductor wafer Wis to be changed to a temperature distribution pattern in which thetemperature in the center part is high, it is necessary only that theheating temperature of the coolant by the heater 15 be controlled bycausing the coolant to circulate in the direction indicated bysolid-line arrows. Conversely, when the temperature distribution of thesemiconductor wafer W is to be changed to a temperature distributionpattern in which the temperature in the outer peripheral part is high,it is necessary only that the coolant be caused to circulate in thedirection indicated by dotted-line arrows.

Therefore, also through the use of this electrostatic chuck S1 as withthe electrostatic chuck S described in FIGS. 1 to 4, it is possible toclearly control the temperature distribution of the semiconductor waferW during plasma etching, with the result that through arbitrarytemperature control it is possible to ensure a uniform temperature inthe plane of the semiconductor wafer or a temperature distribution in aclear state, such as a temperature distribution pattern in which thetemperature in the center portion or a temperature distribution patternin which the temperature in the outer peripheral is high. As a result,this embodiment of the invention can be easily applied to plasmaprocessing in which by canceling out the distribution of reactionproducts the re-adhering of the reaction products to etched surfaces issuppressed, thus contributing greatly to an improvement in the yield ofsemiconductor wafer processing.

In addition, according to this electrostatic chuck S1, installation ofone coolant supply unit 53 is sufficient and, therefore, the compositionof the apparatus can be simplified.

Also, in the case of this electrostatic chuck S1, installation of theheater 15 within the conduit 14 enables space to be effectively utilizedand this construction is very effective also from the standpoint ofthermal efficiency.

Incidentally, in the embodiment shown in FIG. 9, the description wasmade about a case where the heater 15 is of the electric heating type.However, a Peltier element may be used as the heater 15 and in thiscase, it is possible not only to heat the coolant in the conduit 14, butalso cool to this coolant.

Next, FIG. 10 shows the third embodiment of the invention. In thisembodiment, a heater 15 is built in an electrode block 1 to constitutean electrostatic chuck S2. In this embodiment, the heater 15 is cast inthe electrode block 1 by use of casting technology. The heater 15 usedin this case is a heater fabricated by housing a nichrome wire ortungsten wire sheathed with an insulating material, such as alumina in astainless steel tube or a carbon steel, which is called a sheathedheater, etc.

Also, the heater 15 may be of a film structure formed by using multiplelayers of dielectric film 4 in which a tungsten film is sandwiched byouter layers, for example, an alumina/tungsten/alumina structure, and inthis case, the construction may be such that a heater of tungstenfurther serves as the component electrode of an electrostatic chuck.

According to the above embodiment, because the slit for suppressing heattransfer 13 is provided in the electrode block 1, the temperature of thesemiconductor wafer W can be arbitrarily controlled and, at the sametime, thermal efficiency can also be dramatically improved. However, itmight be thought that the rigidity of the electrode block 1 is decreasedby providing the slit for suppressing heat transfer 13.

Therefore, next, an explanation will be given to this embodiment of theinvention in which a decrease in rigidity due to the providing of thisslit is suppressed concerning the case of the electrostatic chuck Sshown in FIG. 1. In this case, as shown in FIG. 11A, the electrostaticchuck S is constituted by an electrode block 1 and a guide member 2. Andin this guide member 2, an O-ring 16 is fitted in the outermostperipheral part and the guide member 2 is tightened to the electrodeblock 1 by means of blots 6, although this is omitted in FIG. 1.

The pressure P of the coolant that flows through the slits 11, 12 isusually 500 KPa or so. However, because this pressure is applied to eachof the slits 11, 12, the electrode block 1 undergoes deformation asdrawn by a broken line in an exaggerated form in FIG. 11B.

Therefore, in order to cope with such deformation and prevent thedeformation, as shown in FIG. 12, it is necessary only that theelectrode block 1 be tightened by means of another bolt 60 from the backside of the guide member 2 in a position corresponding to half theradius of the electrode block 1. This enables deformation to besuppressed as drawn in an exaggerated form in the figure.

According to results of measurement, in a case where only the outermostperipheral part of electrode block 1 with a diameter of 320 mm and athickness of 25 mm, deformation of 0.5 mm or so was observed in thecenter part. However, as shown in FIG. 12, when another bolt 60 wasprovided, deformation scarcely occurred and good results were obtained.

Incidentally, in the case of the above-described embodiment, anelectrostatic chuck S with a better thermal efficiency can be obtainedby fabricating the electrode block 1 from a material of lower thermalconductivity than the guide member 2. In the above embodiment, thematerial for the electrode block 1 is aluminum and the material for theguide member 2 is stainless steel as described above. This meets theabove conditions. Incidentally, the method of tightening the electrodeblock 1 and the guide member 2 together is not limited to the abovescrewing by means of bolts. Other tightening methods, such as brazing,diffusion bonding and electron beam welding, may also be adopted.

Next, as still further embodiments of the invention, an explanation willbe given to an electrostatic chuck that is especially excellent intemperature response. First, FIG. 13 shows the fourth embodiment of theinvention. In the electrostatic chuck S3 of this embodiment, instead offorming slits that serve as coolant flow paths in the electrode block 1,pipes 17, 18 are brazed to the underside of the electrode block 1. Next,FIG. 14 shows the fifth embodiment of the invention. In this figure isshown an electrostatic chuck S4 of the invention in a case where pipes17, 18 that are brazed after being half embedded on the underside of anelectrode block 1 and heaters 20, 21 are individually provided,respectively, for the pipes 15, 16.

In both FIG. 13 and FIG. 14, the pipes 17 form coolant flow paths on theinner peripheral side and the pipes 18 form coolant flow paths on theouter peripheral side. In these cases, the pipes 17, 18 are formed insquare form. The pipes 17, 18 may have an arbitrary polygonal sectionalform and of course they may be ordinary round pipes.

Therefore, first, although the electrostatic chuck S3 shown in FIG. 3 isalmost the same as the electrostatic chuck S shown in FIG. 1, thiselectrostatic chuck S3 is excellent in temperature response because theelectrode block is thin.

Also, the electrostatic chuck S4 shown in FIG. 14 is excellent intemperature response. In this case, because the heaters 20, 21 areprovided on the inner and outer peripheral sides, respectively, of theslit for suppressing heat transfer 13, it is possible to obtain atemperature distribution of finer temperature change by controlling thetemperature by these heaters by means of each power controller 22, 23.As an example, temperature characteristics were measured by causing acoolant to circulate by setting the power supplied to each of theheaters 20, 21 at 300 W and the flow rate of the coolant at 4 l/minute.As a result, it was easy to realize a temperature distribution patternwith a temperature difference of 15° C. in which the temperature in thecenter part is high and a temperature distribution pattern with atemperature difference of 15° C. in which the temperature in the outerperipheral part is high.

In the electrostatic chucks S3, S4 shown in FIGS. 13 and 14, because thepressure of the coolant acts only on the interior of the pipes 17, 18and no direct pressure is applied to the electrode block 1, there is nofear of the occurrence of deformation in the electrode block 1. In theseembodiments, the pipes 17, 18 and heaters 20, 21 may be cast into theelectrode block 1.

Incidentally, although the foregoing applies to the embodiments in whichthe number of the slit for suppressing heat transfer 13 that is formedwithin the block 1 is 1, a plurality of slits for suppressing heattransfer 13 may be provided as required. And in this case, it ispossible to easily realize a temperature distribution with patterns offiner changes and a semiconductor wafer can be controlled to anarbitrary temperature distribution.

With the above-described embodiments, in controlling the electrostaticchuck S, etc. to a prescribed temperature distribution, it is necessarythat a plurality of temperature sensors be provided within the electrodeblock 1. In this case, as described above, because usually thetemperature of the outermost peripheral part of the semiconductor wafershows a tendency to rise relatively in the plane of the semiconductorwafer, by providing temperature sensors in at least three places betweenthe center of the semiconductor wafer and the outer periphery part it ispossible to perform control while monitoring a temperature distributionpattern in which the temperature in the center part is high, atemperature distribution pattern in which the temperature in the outerperipheral part is high, etc.

According to the invention, by providing a slit for suppressing heattransfer in an electrode block and independent temperature controlmechanisms that sandwich this slit on the inner and outer peripheries,it has become possible to control the temperature distribution totemperatures that are independent in the plane of the electrode block.As a result, it has become easy to adapt to changes in temperaturedistribution patterns of semiconductor wafer.

And as a result, it has become possible to accomplish diversifiedprocessing of semiconductor wafers by use of various kinds oftemperature distribution patterns, thus contributing greatly to animprovement in the performance of semiconductor wafers.

Furthermore, according to the invention, the heat-medium flow paths arecomposed of divided members and each divided member is tightened byscrewing, bracing, diffusion bonding and electron beam welding.Therefore, it is possible to easily adapt to deformation of theelectrode block by the pressure of the heat medium.

According to the invention, because the coolant flow paths may also beformed from pipes having a circular or polygonal section,general-purpose parts can be used and the heat capacity of the electrodeblock also decreases. Therefore, an electrostatic chuck and a plasmaprocessing apparatus that are excellent in thermal response can beprovided.

Therefore, according to the plasma processing of this invention, thetemperature control of semiconductor wafers can be arbitrarily set and,at the same time, requirements for uniform etching can be easily met.Therefore, the yield of semiconductor devices can be substantiallyimproved and cost can be sufficiently reduced.

It should be further understood by those skilled in the art that theforegoing description has been made on embodiments of the invention andthat various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

1. A plasma processing apparatus provided with a holding stage of asystem in which a temperature of an electrode block is controlled so asto control a temperature of a semiconductor wafer, wherein saidelectrode block is provided with at least first and second independenttemperature control means on the inner and outer sides thereof and, aslit for suppressing heat transfer is provided in said electrode blockbetween said first and second independent temperature control means. 2.The plasma processing apparatus according to claim 1, wherein said slitfor suppressing heat transfer is formed substantially concentrically. 3.The plasma processing apparatus according to claim 1, wherein a heateris provided on the backside of said electrode block.
 4. The plasmaprocessing apparatus according to claim 1, wherein a heater is built insaid electrode block.
 5. The plasma processing apparatus according toclaim 1, wherein said electrode block is provided, on the surfacethereof, with a dielectric film.
 6. The plasma processing apparatusaccording to claim 1, wherein said electrode block is provided withtemperature sensors and temperature control is performed on the basis ofinformation from said temperature sensors.